A Good Night’s Sleep May Protect Against Dementia

Are you getting a good night’s sleep? Two new studies offer yet more reasons for why you should make sure you do.

In one study, researchers at the University of Rochester, in New York state, found that the brain sweeps away waste and toxins during sleep. In the other, researchers at Johns Hopkins University, in Baltimore, found that poor-quality sleep is linked to the buildup of toxins that seem to contribute to Alzheimer’s disease. Taken together, these studies show how sleep could be crucial to brain health.

The University of Rochester study, published on Oct. 18 in the journal Science, found that the flow of cerebrospinal fluid increases dramatically in the brain during sleep, cleaning out toxins such as amyloid beta-protein – the plaques that are the hallmark of Alzheimer’s disease. The cleaning process is “like a dishwasher,” study author Maiken Nedergaard, M.D., told NPR.

During sleep, brain cells “shrink” by 60 percent, allowing waste to be reduced more effectively. (No wonder I’m in a fog when the kids or dogs drag me from bed in the middle of the night.) Last year Nedergaard and her colleagues discovered a system of waste removal that is unique to the brain. This cleaning system takes a lot of energy and may explain why animals need sleep and become sick or even die if they don’t get it. Scientists had known that the brain uses a lot of energy during sleep, but it wasn’t until they could utilize new technology to study the brains of sleeping mice that they could understand why.

The Johns Hopkins study, published today in JAMA Neurology, examined the link between sleep and amyloid-beta buildup in the brain. The researchers compared the self-reported sleep habits of older adults, average age 76, who took part in the long-running Baltimore Longitudinal Study of Aging, with the amount of amyloid-beta as measured by PET scans. The scientists found that those who reported the least sleep with the poorest sleep quality had more of the toxic plaque in the brain.

The researchers still can’t say much about cause and effect: Is poor sleep helping to cause Alzheimer’s disease? Or are people not sleeping well because they are developing the disease? The good news, said Adam Spira, Ph.D., lead author of the study and an assistant professor in the Department of Mental Health at the Johns Hopkins Bloomberg School of Public Health, is that we can help older people sleep better.